feat: migrate to react 19 (#3107)

apps/remix/app/entry.client.tsx

@@ -31,6 +31,26 @@ function initPosthog() {
   }
 }
 
+/**
+ * Surfaces hydration recoveries (React 19 discards the server HTML and
+ * re-renders on the client instead of dying) so we can track how often
+ * extensions/early clicks interfere with hydration in the wild.
+ */
+function onRecoverableError(error: unknown, errorInfo: { componentStack?: string }) {
+  console.error('[hydration] recovered from error', error, errorInfo.componentStack);
+
+  if (extractPostHogConfig()) {
+    void import('posthog-js').then(({ default: posthog }) => {
+      if (posthog.__loaded) {
+        posthog.capture('$hydration_recoverable_error', {
+          message: error instanceof Error ? error.message : String(error),
+          componentStack: errorInfo.componentStack,
+        });
+      }
+    });
+  }
+}
+
 async function main() {
   const locale = detect(fromHtmlTag('lang')) || 'en';
 
@@ -44,6 +64,7 @@ async function main() {
           <HydratedRouter />
         </I18nProvider>
       </StrictMode>,
+      { onRecoverableError },
     );
   });